Cutting tool configuration for a feller-buncher

ABSTRACT

An apparatus for felling and bunching trees is disclosed. The apparatus includes a frame and a yoke pivotably connected to the frame. The apparatus further includes a tool support pivotably connected to the yoke at a pivot axis and a cutting tool supported by the tool support. The cutting tool has a leading edge LE which is advanced toward the trees during a felling operation. The cutting tool further has a trailing edge TE which lags behind the leading edge LE when the leading edge LE is advanced toward the trees during the felling operation. The apparatus yet further includes a tilt cylinder positioned between the frame and the tool support. The tilt cylinder is movable between an extended tilt position and a retracted tilt position. The leading edge LE is moved closer to the ground when the tilt cylinder is moved from the retracted tilt position to the extended tilt position. The leading edge LE is moved away from the ground when the tilt cylinder is moved from the extended tilt position to the retracted tilt position. A first distance D1 is defined between the leading edge LE and the trailing edge TE. The pivot axis defines a vertical plane that intersects the cutting tool at a line V1. A second distance D2 is defined between the line V1 and the leading edge LE. And the ratio of the second distance to the firs distance is less than or equal to 0.50.

This application claims the benefit of U.S. Provisional Application Ser.No. 60/111,429, filed Dec. 8, 1998.

TECHNICAL FIELD OF THE INVENTION

The present invention relates generally to a feller-buncher, and morespecifically a cutting tool configuration for a feller-buncher.

BACKGROUND OF THE INVENTION

Feller-bunchers are used to fell, or cut down, a number of trees andthen to bunch the trees together for transport. The bunched trees arethen transported to a storage site for further processing. Typicalfeller-bunchers are articulated machines that include a front frame anda rear frame that are pivotally coupled by a hitch. The hitch allows thefront frame to pivot relative to the rear frame so as to steer thefell-buncher. The front frame includes a front axle having a pair ofwheels mounted thereon, and the rear frame includes a rear axle alsohaving a pair of wheels mounted thereon.

The feller-buncher further includes a work tool that cuts down trees andsecures the cut trees to the feller-buncher. The work tool is mounted ona yoke that is pivotally attached to the front frame of thefell-buncher. The yoke can be raised or lowered relative to front framein order to position the work tool during operation. The work toolincludes a rotating saw which is used to cut down trees. In addition,the work tool has a number of hydraulically powered work arms which areused to secure the trees within the work tool after the trees have beencut down.

The feller-buncher further includes a tilt cylinder which is operable topivot the work tool relative to the yoke. To unload the trees from thework tool, the work tool is tilted forward relative to the yoke and thework arms release the trees from the work tool. A disadvantage offeller-bunchers that have heretofore been designed is that as the worktool is tilted forward, a leading edge of the rotating saw is movedsignificantly closer to the ground. If the rotating saw contacts a hardobject, such as a rock, the rotating saw can become damaged. Such damagemay require expensive and time consuming repairs to the rotating saw. Tocompensate for moving the rotating saw closer to the ground, theoperator must raise the work tool to provide additional clearancebetween the rotating saw and the ground as the work tool is tiltedforward. However, raising the work tool has two disadvantages. First,raising the work tool raises the center of gravity of the entirefeller-buncher thereby decreasing the stability of the feller-buncher.Second, raising the work tool adds an extra step to the unloadingprocess, which can potentially slow down the unloading process and leadto reduced productivity from the feller-buncher.

What is needed therefore is an apparatus and method for felling andbunching trees which overcome one or more of the above-mentioneddrawbacks.

DISCLOSURE OF THE INVENTION

In accordance with a first embodiment of the present invention, there isprovided an apparatus for felling and bunching trees. The apparatusincludes a frame and a yoke pivotably connected to the frame. Theapparatus further includes a tool support pivotably connected to theyoke at a pivot axis and a cutting tool supported by the tool support.The cutting tool has a leading edge LE which is advanced toward thetrees during a felling operation. The cutting tool further has atrailing edge TE which lags behind the leading edge LE when the leadingedge LE is advanced toward the trees during the felling operation. Theapparatus yet further includes a tilt cylinder positioned between theframe and the tool support. The tilt cylinder is movable between anextended tilt position and a retracted tilt position. The leading edgeLE is moved closer to the ground when the tilt cylinder is moved fromthe retracted tilt position to the extended tilt position. The leadingedge LE is moved away from the ground when the tilt cylinder is movedfrom the extended tilt position to the retracted tilt position. A firstdistance D1 is defined between the leading edge LE and the trailing edgeTE. The pivot axis defines a vertical plane that intersects the cuttingtool at a line V1. A second distance D2 is defined between the line V1and the leading edge LE. And the ratio of the second distance to thefirs distance is less than or equal to 0.50.

In accordance with a second embodiment of the present invention, thereis provided an apparatus for felling and bunching trees. The apparatusincludes a yoke pivotably connected to the frame and a tool supportpivotably connected to the yoke at a pivot axis. The apparatus furtherincludes a cutting tool supported by the tool support. The cutting toolhas a leading edge LE which is advanced toward the trees during afelling operation and a trailing edge TE which lags behind the leadingedge LE when the leading edge LE is advanced toward the trees during thefelling operation. The apparatus still further includes a tilt cylindermovable between an extended tilt position and a retracted tilt position.The cutting tool is caused to tilt when the tilt cylinder is movedbetween the extended tilt position and the retracted tilt position. Afirst distance D1 is defined between the leading edge LE and thetrailing edge TE. The pivot axis defines a vertical plane thatintersects the cutting tool at a line V1. A second distance D2 isdefined between the line V1 and the leading edge LE. The ratio of thesecond distance to the first distance is less than or equal to 0.50.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a fell-buncher which incorporates thefeatures of the present invention therein;

FIG. 2 is a side elevational view of the feller-buncher of FIG. 1;

FIG. 3 is an enlarged top elevational view of cutting tool of thefeller-buncher of FIG. 1; and

FIG. 4 is a schematic view of the hydraulic system of the feller buncherof FIG. 1.

BEST MODE FOR CARRYING OUT THE INVENTION

While the invention is susceptible to various modifications andalternative forms, a specific embodiment thereof has been shown by wayof example in the drawings and will herein be described in detail. Itshould be understood, however, that there is no intent to limit theinvention to the particular form disclosed, but on the contrary, theintention is to cover all modifications, equivalents, and alternativesfalling within the spirit and scope of the invention as defined by theappended claims.

Referring now to FIGS. 1 and 2, there is shown a feller-buncher 10 thatincorporates the features of the present invention therein. Thefeller-buncher 10 includes front frame 12 and a rear frame 14. The frontframe 12 is pivotally connected to the rear frame 14 via a hitch 16. Inparticular, the hitch 16 allows the front frame 12 to pivot relative tothe rear frame 14 in the general direction of arrows 18 and 20 of FIG.1.

The front frame 12 is supported by a front axle 22. Two wheels 24 aremounted to the front axle 22. In particular, the front axle 22 and thewheels 24 can rotate relative to the front frame 12 in the generaldirection of arrows 26 and 28. A front hydraulic motor 30, shown in FIG.2, is supported by the front frame 12 and operatively coupled to thefront axle 22. The front hydraulic motor 30 is a bidirectional motorwhich allows the front hydraulic motor 30 to drive the front axle in thegeneral direction of arrow 26 or 28. Driving the front axle 22 in thegeneral direction of arrow 26 advances the front frame 12 in the generaldirection of arrow 100 whereas driving the front axle 22 in the generaldirection of arrow 28 advances the front frame 12 in the generaldirection of arrow 99. The front frame 12 further supports a cab 32which includes a seat 34 (shown in FIG. 1) for an operator of thefeller-buncher 10. The cab 32 further includes a number of controls 36(shown in FIG. 1) which are manipulated by the operator to controlvarious operations of the feller-buncher 10.

The rear frame 14 is similarly supported by a rear axle 38. Two wheels40 are mounted to the rear axle 38. In particular, the rear axle 38 andthe wheels 40 can rotate relative to the rear frame 14 in the generaldirection of arrows 26 and 28. A rear hydraulic motor 42 is supported bythe rear frame 14 and operatively coupled to the rear axle 38. The rearhydraulic motor 42 is a bi-directional motor which allows the rearhydraulic motor 42 to drive the rear axle 38 in the general direction ofarrow 26 or 28. Driving the rear axle 38 in the general direction ofarrow 26 advances the rear frame 14 in the general direction of arrow100 whereas driving the rear axle 38 in the general direction of arrow28 advances the rear frame 14 in the general direction of arrow 99.

The feller-buncher 10 further includes an engine 44. The engine 44 ismounted on the rear frame 14. The engine 44 generates mechanical energywhich is transferred to a pump assembly 50. The pump assembly 50includes a number of pumps which convert the mechanical energy of theengine 44 to hydraulic energy which is used to power various hydrauliccomponents of the fell-buncher 10, such as the front hydraulic motor 30and the rear hydraulic motor 42. In particular, the pump assembly 50includes a pump housing 51, a first hydraulic pump 52, and a secondhydraulic pump 54. Both the first hydraulic pump 52 and the secondhydraulic pump 54 are contained within the pump housing 51. Each of thefirst hydraulic pump 52 and the second hydraulic pump 54 is a variabledisplacement pump that can provide a variable volume of pressurizedfluid to the hydraulically powered components of the feller-buncher 10.

The feller-buncher 10 further includes a yoke 56 pivotally attached tothe front frame 12. In particular, the yoke 56 rotates relative to thefront frame 12 in the general direction of arrows 26 and 28 about a pin57. A pair of lift cylinders 58 are interposed between the front frame12 and the yoke 56. As the lift cylinders 58 are extended, the liftcylinders 58 cause the yoke 56 to move in the general direction of arrow58 which causes the yoke to pivot about the front frame 12 in thegeneral direction of arrow 26. On the other hand, as the lift cylinders58 are retracted, the lift cylinders 58 cause the yoke 56 to move in thegeneral direction of arrow 60 which causes the yoke 56 to pivot aboutthe front frame 12 in the general direction of arrow 28.

A work tool 62 is pivotally mounted to the yoke 56. To this end, thework tool 62 includes a pair of pins 64 which are recieved in one of arespective pin aperture 66 defined in the yoke 56. The pins 64 allow thework tool 62 to pivot about the yoke in the general direction of arrows26 and 28. A tilt cylinder 68 is interposed between the front frame 12and an upper portion of the work tool 62. As the tilt cylinder 68 isextended, the tilt cylinder 68 urges the upper portion of the work toolin the general direction of arrow 100 which causes the work tool 62 torotate in the general direction of arrow 26 about the pin apertures 66of the yoke 56. Conversely, as the tilt cylinder 68 is retracted, thetilt cylinder 68 urges the upper portion of the work tool in the generaldirection of arrow 99 which causes the work tool 62 to rotate in thegeneral direction of arrow 28 about the pin apertures 66 of the yoke 56.

Referring now to FIGS. 2 and 3, the work tool 62 includes a supportmember 69 which supports various components of the work tool 62. Thework tool 62 further includes a cutting tool 70 which is rotatablysecured to a lower portion of the support member 69 such that thecutting tool 70 can rotate in the general direction of arrow 20. Thecutting tool 70 is a rotating saw having number of blades, or cuttingteeth 72, defined thereon (see FIG. 3). A saw motor 74 is secured to thesupport member 69 and is operative to rotate the cutting tool 70 in thegeneral direction of arrow 20. In particular, the saw motor 74 is ahydraulic motor which is powered by one or more of the first hydraulicpump 52 and the second hydraulic pump 54. During a felling operation,the feller-buncher 10 is advanced in the general direction of arrow 100and the cutting tool 70 is rotated in the general direction of arrow 20.As the cutting tool 70 is rotated in the general direction of arrow 20,the cutting teeth 72 cut through any trees that come into contact withthe cutting tool 70. The cutting tool 70 further includes a blade guard71 which covers the side, rear, and underneath portions of the rotatingcutting tool 70 that are not advanced into a tree during a fellingoperation.

Referring again to FIG. 3, the cutting tool 70 defines a leading edgeLE. The leading edge LE is a line that defines the furthest point of thecutting tool 70 in the general direction of arrow 100. The leading edgeLE defines the most forward point at which the cutting tool 70 can beginto cut into trees as the feller-buncher 10 is advanced in the generaldirection of arrow 100. Similarly, the cutting tool 70 defines atrailing edge TE. The trailing edge TE is furthest point of the cuttingtool 70 in the general direction of arrow 99. The trailing edge TE is aline that defines the most rearward point of the cutting tool 70. Itshould be appreciated that as the tilt cylinder 68 is extended, the worktool 62 rotates about the pins 64 in the general direction of arrow 26so as to position the leading edge LE closer to the ground. On the otherhand, as the tilt cylinder 68 is retracted, the work tool 62 rotatesabout the pins 64 in the general direction of arrow 28 so as to positionthe leading edge LE farther from the ground.

In addition, the pivot axis of the work tool 62 about the pin apertures66 of yoke 56 defines a vertical plane, and the vertical planeintersects the work tool 70 to define a line V1. A first distance D1 isdefined as the distance between the leading edge LE and the trailingedge TE. A second distance D2 is defined as the distance between theline V1 and the leading edge LE. The second distance D2 is less than onehalf of the first distance D1. Preferably, the second distance D2 isless than one fourth of the distance D1. It should be appreciated thatreducing the distance D2 decreases the vertical movement of the leadingedge LE of the cutting tool 70 as the work tool is rotated relative tothe yoke 56 in the general direction of arrows 18 and 20.

Referring again to FIG. 2, the leading edge LE and the trailing edge TEdefine a line H1. The line H1 intersects with the ground to form anangle θ1. It should be appreciated that the front frame 12, yoke 56,work tool 62, and tilt cylinder 68 are advantageously configured tomaintain the angle θ1 substantially the same as the lift cylinders 58are moved between the extended and the retracted positions. Thus,because of the configuration of the tilt cylinder 68 relative to thework tool 62, the tilt cylinder prevents the rotation of the work tool62 relative to the ground and the angle θ1 is remains substantially thesame as the lift cylinders 58 are retracted.

On a similar note, because of the configuration of the tilt cylinder 68relative to the work tool 62, the tilt cylinder 68 prevents the rotationof the work tool 62 relative to the ground and the angle θ1 is remainssubstantially the same as the lift cylinders 58 are extended. Thus, theangle θ1 is maintained at a substantially constant value as the liftcylinders 56 are extended and retracted.

Referring again to FIGS. 1 and 2, the work tool 62 further includes anumber of work arms 76, 77 (shown in FIGS. 2 and 3) which are rotatablysecured to the support member 69. An arm cylinder 78 (shown in FIG. 4)is operable to move the work arms 76, 77 between a receiving position inwhich trees can be advanced between the work arms 76, 77 and a securingposition in which trees are secured to the support member 69. Inparticular, as the arm cylinder 78 is extended, the work arm 76 rotatesin the general direction of arrow 20 from the receiving position, shownin FIG. 4, to the securing position, not shown. Concurrently, as the armcylinder 78 is extended, the work arm 77 rotates in the generaldirection of arrow 18 from the receiving position, shown in FIG. 4, tothe securing position, not shown, thereby securing any trees within thework tool 62.

Once the trees have been felled, or cut, by the cutting tool 70 andsecured within the work tool 62 by the work arms 76, 77, the trees aretransported to a site where the trees are stored for further processing.To remove the trees from the work tool 62, (i) the trees must beunsecured from the work tool 62 and (ii) the work tool 62 must be tiltedforward in the general direction of arrow 26 so that the trees will fallto the ground in front of the feller-buncher 10. To unsecure the treesfrom the work tool 62, the arm cylinder 78 is retracted causing the workarm 76 to rotate in the general direction of arrow 18 from the securingposition, not shown, to the receiving position, shown in FIG. 4.Concurrently, as the arm cylinder 78 is retracted, the work arm 77rotates in the general direction of arrow 20 from the securing position,not shown, to the receiving position, shown in FIG. 4, thereby releasingthe trees previously secured within the work tool 62.

To tilt the work tool 62 forward, the tilt cylinder 68 is extendedthereby causing the work tool 62 to rotate relative to the yoke 56 inthe general direction of arrow 26. It should be appreciated that asignificant advantage of the present invention is that as the work tool62 is tilted forward in the general direction of arrow 26, the leadingedge LE (shown in FIG. 3) of the cutting tool 70 is not movedsignificantly closer to the ground than prior to the tilting of the worktool 62. In feller-bunchers that have heretofore been designed, as thework tool is tilted forward, the leading edge of the work tool is urgedtoward the ground thereby making it likely that the work tool could bedamaged by contacting the ground. To avoid damaging the work tool,operators of prior art feller bunchers would raise the yoke prior totilting the work tool, thus making the feller buncher less stable.

The present invention has the advantages of (i) reducing the probabilitythat the cutting tool 70 of the work tool 62 will be damaged during anunloading operation, (ii) being easier for the operator to operatebecause the unloading operation does not require the additional actionof raising the work tool 62 when the work tool 62 is tilted forward inthe general direction of arrow 26, and (iii) increasing the stability ofthe feller-buncher 10 during unloading operations because the work tool62 is maintained lower to the ground.

Referring now to FIG. 4, there is shown a schematic view of thehydraulic system of the fell-buncher 10. The feller-buncher 10 furtherincludes a valve assembly 80. Pressurized fluid from the first hydraulicpump 52 is supplied to the valve assembly 80 via the fluid line 82 andpressurized fluid from the second hydraulic pump 54 is supplied to thevalve assembly 80 via the fluid line 84. From the valve assembly 80,pressurized hydraulic fluid is supplied to the various hydrauliccomponents of the feller-buncher 10. Pressurized hydraulic fluid is usedto power the front hydraulic motor 30 and the rear hydraulic motor 42 soas to propel the feller buncher 10 in the general direction of arrows 99and 100.

In addition, pressurized hydraulic fluid is used to steer thefeller-buncher 10. To this end, the feller-buncher 10 further includes aright steering cylinder 86 and a left steering cylinder 88 which areoperable to rotate the front frame 12 relative to the rear frame 14about the hitch 16 in the general direction of arrows 18 and 20.Pressurized hydraulic fluid is advanced from the valve assembly 80 tothe right steering cylinder 86 via the fluid line 90 whereas pressurizedhydraulic fluid is advanced from the valve assembly 80 to the leftsteering cylinder 88 via the fluid line 92. To steer to thefeller-buncher 10 to the right, the right steering cylinder 86 isretracted and the left steering cylinder 88 is extended. To steer to thefeller-buncher 10 to the left, the right steering cylinder 86 isextended and the left steering cylinder 88 is retracted.

Pressurized hydraulic fluid from the valve assembly 80 is also used topower other components of the feller-buncher 10. In particular,pressurized fluid in the fluid line 94 is used to power the liftcylinders 58, pressurized fluid in the line 96 is used to power the tiltcylinder 98, pressurized fluid in the fluid line 102 is used to powerthe saw motor 74, and pressurized fluid in the line 104 is used to powerthe arm cylinder 78. In addition, hydraulic pressure from the firsthydraulic pump 52 and second hydraulic pump 54 may be used to powerother hydraulic devices such as brakes (not shown) and lockingdifferentials (not shown) on the front axle 22 and the rear axle 38.

It should be appreciated that a significant advantage of the presentinvention is that a single hydraulic system is used to power both thedrive and non-drive components of the feller-buncher 10. Infell-bunchers that have heretofore been designed, the front axles andrear axles are typically driven by a mechanical drive system. Thismechanical drive systems include a drop box which splits mechanicalpower between the front and rear axles and a drive shaft and universaljoint which transfers mechanical power across the hitch. Each of thesemechanical components are high maintenance items which are expensive tooperate. By using the hydraulic drive motors 30, 42, the drop box, driveshaft, and universal joint can be eliminated.

In addition, prior art work machines, such as feller-bunchers, which usehydraulics to drive the wheels, typically have a separate hydraulicsystem for the drive components and the non-drive components such aslift cylinders and tilt cylinders. Having two separate hydraulic systemsincreases the complexity of the work machine. In addition, theseparating the hydraulic systems prevents any transfer of hydraulicpower from one system to the other.

Industrial Applicability

In operation, the feller-buncher 10 is maneuvered toward a group oftrees. In particular, pressurized hydraulic fluid from the firsthydraulic pump 52 and the second hydraulic pump 54 is supplied to thefront hydraulic motor 30 and the rear hydraulic motor 42 to propel thefeller-buncher 10 in the general direction of arrows 99 or 100.Furthermore, pressurized hydraulic fluid is advanced to the rightsteering cylinder 86 and the left steering cylinder 88 to steer thefeller-buncher 10 toward the trees in the general direction of arrows 18and 20.

As the feller buncher approaches the trees, pressurized hydraulic fluidis advanced to the saw motor 74 which causes the cutting tool 70 torotate in the general direction of arrow 20. As the feller-buncher 10advances toward the trees, the cutting teeth 72 of the cutting tool 70cut through the trunks of trees. Concurrently, the work arms 76, 77 aremoved from a receiving position to a securing position so as to securethe trees within the work tool 62.

Subsequently, the feller-buncher 10 moves to a site where the trees areto be unloaded from the fell-buncher 10 for further processing. Onceagain, pressurized hydraulic fluid from the first hydraulic pump 52 andthe second hydraulic pump 54 is supplied to the front hydraulic motor 30and the rear hydraulic motor 42 to propel the feller-buncher 10 in thegeneral direction of arrows 99 or 100. To steer the feller-buncher 10,pressurized hydraulic fluid is advanced to the right steering cylinder86 and the left steering cylinder 88 to steer the feller-buncher 10 inthe general direction of arrows 18 and 20.

To unload the trees from within the work tool 62, the trees must firstbe unsecured from the work tool 62. To unsecure the trees from the worktool 62, the arm cylinder 78 is retracted causing the work arms 76, 77to move from the securing position to the receiving position therebyreleasing the trees from the work tool 62. To move the trees from thework tool 62 to the site, the work tool 62 must be tilted forward in thegeneral direction of arrow 26 so that the trees will fall to the groundin front of the feller-buncher 10. To tilt the work tool 62, the tiltcylinder 68 must be extended so as to cause the work tool 62 to rotatein the general direction of arrow 26.

It should be appreciated that as the work tool 62 rotates relative tothe yoke 56, the leading edge LE of the cutting tool 70 does not movesubstantially closer to the ground, thus reducing the likelihood thatthe cutting tool 70 would come into contact with an object, such as arock, as the feller-buncher 10 is unloaded.

While the invention has been illustrated and described in detail in thedrawings and foregoing description, such illustration and description isto be considered as exemplary and not restrictive in character, it beingunderstood that only the preferred embodiment has been shown anddescribed and that all changes and modifications that come within thespirit of the invention are desired to be protected.

I claim:
 1. An apparatus for felling and bunching trees, comprising:aframe; a yoke pivotably connected to said frame; a tool supportpivotably connected to said yoke at a pivot axis; a cutting toolsupported by said tool support, said cutting tool having (i) a leadingedge LE which is advanced toward said trees during a felling operation,(ii) a trailing edge TE which lags behind said leading edge LE when saidleading edge LE is advanced toward said trees during said fellingoperation; and a tilt cylinder positioned between said frame and saidtool support, said tilt cylinder being movable between (i) an extendedtilt position and a retracted tilt position, (ii) said leading edge LEis moved closer to the ground when said tilt cylinder is moved from saidretracted tilt position to said extended tilt position, and (iii) saidleading edge LE is moved away from the ground when said tilt cylinder ismoved from said extended tilt position to said retracted tilt position,wherein (i) a first distance D1 is defined between said leading edge LEand said trailing edge TE, (ii) said pivot axis defines a vertical planethat intersects said cutting tool at a line V1, (iii) a second distanceD2 is defined between said line V1 and said leading edge LE, and (iv)D2/D1≦0.50.
 2. The apparatus of claim 1, wherein D2/D1≦0.25.
 3. Theapparatus of claim 1, further comprising a lift cylinder which ismovable between a lower position and an upper position, wherein:saidleading edge LE and said trailing edge TE define a line H1 whichintersects the ground to form an angle θ1, and said frame, said yoke,said tilt cylinder, and said lift cylinder are positioned in relation toeach other such that said angle θ1 remains substantially the same assaid lift cylinder is moved between said lower position and said upperposition.
 4. The apparatus of claim 1, wherein said cutting toolincludes a rotating saw blade.
 5. The apparatus of claim 4, furthercomprising a number of work arms which are movable to grasp said trees,wherein:said number of work arms are supported by said tool support. 6.The apparatus of claim 5, further comprising a number of hydraulic pumpsfor supplying pressurized hydraulic fluid, wherein:said tilt cylinder,said lift cylinder, said cutting tool, and said work arms are each influid communication with at least one of said number of hydraulic pumps.7. The apparatus of claim 1, wherein:said cutting tool includes arotating saw blade, and said pivot axis is positioned vertically abovesaid rotating saw blade.
 8. The apparatus of claim 7, wherein:said toolsupport includes a blade guard, said blade guard covers said trailingedge TE of said rotating saw blade, and said blade guard is pivotablyattached to said yoke.
 9. An apparatus for felling and bunching trees,comprising:a yoke pivotably connected to a frame; a tool supportpivotably connected to said yoke at a pivot axis; a cutting toolsupported by said tool support, said cutting tool having (i) a leadingedge LE which is advanced toward said trees during a felling operation,(ii) a trailing edge TE which lags behind said leading edge LE when saidleading edge LE is advanced toward said trees during said fellingoperation; and a tilt cylinder movable between an extended tilt positionand a retracted tilt position, wherein said cutting tool is caused totilt when said tilt cylinder is moved between said extended tiltposition and said retracted tilt position, wherein (i) a first distanceD1 is defined between said leading edge LE and said trailing edge TE,(ii) said pivot axis defines a vertical plane that intersects saidcutting tool at a line V1, (iii) a second distance D2 is defined betweensaid line V1 and said leading edge LE, and (iv) D2/D1≦0.50.
 10. Theapparatus of claim 9, wherein D2/D1≦0.25.
 11. The apparatus of claim 9,further comprising a lift cylinder which is movable between a lowerposition and an upper position, wherein:said leading edge LE and saidtrailing edge TE define a line H1 which intersects the ground to form anangle θ1, and said frame, said yoke, said tilt cylinder, and said liftcylinder are positioned in relation to each other such that said angleθ1 remains substantially the same as said lift cylinder is moved betweensaid lower position and said upper position.
 12. The apparatus of claim9, wherein said cutting tool includes a rotating saw blade.
 13. Theapparatus of claim 12, further comprising a number of work arms whichare movable to grasp said trees, wherein:said number of work arms aresupported by said tool support.
 14. The apparatus of claim 13, furthercomprising a number of hydraulic pumps for supplying pressurizedhydraulic fluid, wherein:said tilt cylinder, said lift cylinder, saidcutting tool, and said work arms are each in fluid communication with atleast one of said number of hydraulic pumps.
 15. The apparatus of claim9, wherein:said cutting tool includes a rotating saw blade, and saidpivot axis is positioned vertically above said rotating saw blade. 16.The apparatus of claim 15, wherein:said tool support includes a bladeguard, said blade guard covers said trailing edge TE of said rotatingsaw blade, and said blade guard is pivotably attached to said yoke.